Conducting foil for conductively connecting electric and/or electronic components

ABSTRACT

In a conductor foil for conductively connecting electrical and/or electronic components, the conductor foil including printed circuit traces, insulated to the outside and applied on a non-conductive, elastically malleable carrier foil. The conductive foil also includes soldering surfaces connected to the printed circuit traces, for soldering to electric terminals of components, in addition, the conductor foil includes feed line segments through which the printed circuit traces are led to the soldering surfaces, in order, in response to shaking stresses, to avoid damage to the soldering points by vibrations transmitted by the feed line segments. Furthermore, the conductor foil has stiffening segments branching off from the feed line segments, the stiffening segments, in response to shaking stresses, causing a force diversion of the vibrations onto the stiffening segments via the feed line segment movable end, which is not connected to the soldering surfaces.

FIELD OF THE INVENTION

The present invention relates to a conductor foil for conductivelyconnecting electrical and/or electronic components.

BACKGROUND INFORMATION

It is known to use conductor foils for electrically connectingelectrical or electronic components. The conductor foils have amultilayer structure, printed circuit trace patternings, insulated tothe outside, being applied to a nonconductive carrier foil. For example,it is known to apply thin copper printed circuit traces onto a carrierfoil made of polyimide and to cover them with a further carrier foil.The printed circuit traces are conductively connected to the solderingsurfaces arranged on the conductor foil for hard-soldering to theelectrical terminals of components. Conductor foils of this type areemployed, for example, near automobile engines or transmission units.Thus it is known, for example, to integrate a hybrid circuit in thehousing of a clutch actuator, the hybrid circuit being connected, via aconductor foil, to various valves for regulating compressed air as wellas to an eddy current sensor and to a plug-in part for connection toexternal cables. The hybrid circuit has a plug connector for thispurpose, whose connector pins are soldered to the soldering surfaces ofthe conductor foil, which are designed as soldering eyelets. Theelastically malleable conductor foils have great strength in the face ofvibration stresses, but the most extreme shaking stresses arising inunits of this type with acceleration up to 50 g, exert extremely heavystresses on the soldering surfaces of the conductor foil. Vibrationstresses, which are transmitted to the plug connector via a vibratingfeed line segment of the conductor foil, can lead to the solderingpoints breaking or individual connecting pins being broken from the plugconnector.

SUMMARY OF THE INVENTION

The conductor foil of the present invention has an advantage that theforces exerted by the vibrations of a feed line segment of the conductorfoil are not transmitted to the soldering surfaces of the conductorfoil, and, in this way, damage to the soldering points is avoided andthe reliability of the electrical connection is increased. This isachieved by providing for at least one stiffening segment branching offfrom the feed line segment, the stiffening segment bringing about adiversion of the forces of vibrations transmitted to the stiffeningsegment, via the movable end of the feed line segment, which is notconnected to the soldering surfaces.

It is particularly advantageous, as a means of force diversion, toarrange on the conductor foil at least one reinforcing layer to stiffenthe elastically malleable conductor foil, the stiffening layer coveringthe feed line segment in the bonding area of the feed line segment andextending at least partly over the stiffening segment. The reinforcinglayer can be applied to the conductor foil using conventional productionmethods in a simple manner.

Furthermore, it is advantageous to integrate a connecting point into thestiffening segment, the connecting point being spatially separate fromthe soldering points of the feed line segment and able to be connectedto a connecting means. The connecting point can be affixed to a housingpart, for example, using a screw or a corresponding aid. Then, inresponse to vibration stresses, the forces of the conductor foil feedline segment, acting upon the stiffening segment, are transmitted to thescrew connected to the connecting point.

The reinforcing layer can advantageously be an additional polyimidelayer and/or a metallic layer applied on the conductor foil, e.g., atin-coated copper layer. These layers can advantageously produce anabrasion protection effect for the conductor foil at such points wherethe conductor foil contacts housing parts. During the production of theconductor foil, the tin-coated copper layer, together with the solderingsurfaces provided for the connection to the components, can be producedin a simple manner.

It is particularly advantageous to provide the connecting point as aground for the components connected to the soldering points. For thispurpose, provision is made for a further elastically malleable foilsegment containing a single grounding printed circuit trace andconnecting a soldering surface, soldered to a grounding pin of thecomponent, to the connecting point. In the case of relative movement,arising in response to vibration, between the connecting point, affixedto a housing part, and the soldering points of the components, no forceis transmitted by the elastic foil segment to the sensitive solderingpoints.

It is also advantageous to design the edge of the reinforcing layer,facing the movable part of the feed line segment, with a notchedcontour, to obtain a smooth transition from the reinforcing area to theelastically malleable area of the feed line segment, and to avoid abreak in the printed circuit trace at this location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows an inner layer of a conductor foil having printed circuittrace patternings.

FIG. 1b shows a top view of the conductor foil.

FIG. 1c shows a bottom view of the conductor foil.

FIG. 2 shows a cross sectional view of a part of the conductor foil.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1a, 1b and 1c show a cut-away portion of a conductor foil having afeed line segment 1. As illustrated in FIG. 1a, the conductor foil has,in a middle layer, thin copper printed circuit traces 7, 7', and 7",which, on the upper and lower sides, are covered by an elasticallymalleable polyimide layer 9, 10. The layered design of the conductorfoil is schematically depicted in FIG. 2. Printed circuit traces 7 offeed line segment 1 are connected to soldering surfaces 8, which areprovided for the soldering to the connecting pins of an undepictedelectronic circuit carrier. Soldering surfaces 8 are designed in theshape of soldering eyelets. The printed circuit traces can be connectedto soldering surfaces 8 on the upper side (FIG. 1b), for example, viametal-coated through holes, in a conventional manner. When the conductorfoil is connected to a circuit carrier, e.g., a hybrid circuit, theconnecting pins of the hybrid circuit are led through the through holesand are soldered to the soldering eyelets. In response to shaking stresson the arrangement, end 3 of feed line segment 1, which is freelymovable, elastically malleable, and connected to the other feed linesegments of the conductor foil, oscillates or vibrates. FIGS. 1a, 1b and1c show a stiffening segment 2 branching off from the feed line segment.Stiffening segment 2 has a large-surface printed circuit trace 7" on theinner layer of the conductor foil (FIG. 1a). To large-surface printedcircuit trace 7" is connected a further printed circuit trace 7', whichis connected to one of soldering surfaces 8 on feed line segment 1, viaa narrow elastically malleable foil segment 14. As illustrated in FIG.1b and FIG. 2, provision is made on the upper side of the conductor foilfor a copper layer 12, which is covered by a tin layer 13. Thesemetallic layers constitute a reinforcing layer, which increases therigidity of the conductor foil in the area of stiffening segment 2.Metallic layers 12, 13 extend over entire stiffening segment 2 and overthe part of feed line segment 1 which constitutes bonding area 5 ofstiffening segment 2. On the reverse side of the conductor foil, asillustrated in FIG. 1c and FIG. 2, an additional polyimide layer 11 isapplied onto stiffening area 5, the polyimide layer at least partiallycovering the stiffening area. The polyimide layer also extends overbonding area 5 of feed line segment 1 and stiffening segment 2, and ithas a greater thickness than polyimide layer 10. Arranged in stiffeningsegment 2 is a connecting point 6 shaped as a circular opening. Theinner wall of the opening is connected, via a through-plating, toprinted circuit trace 7' and printed circuit trace 7". Stiffeningsegment 2 can be screwed, for example, to a housing part, using a screwpassing through this opening. Via printed circuit trace 7', a ground isthen simultaneously achieved, both of soldering surface 8, connected tothis printed circuit trace, and of the connecting pin of the hybridcircuit, connected thereto. When the arrangement undergoes vibration orshaking stresses, the force of acceleration is now exerted via freelymovable end 3 of feed line segment 1 onto reinforcing layers 11, 12, and13, and is diverted from them to connecting point 6, so that solderingsurfaces 8 are relieved of strain and no great stresses are transmittedto them. At the same time, elastic foil segment 14 having the groundingprinted circuit trace permits relative movement between connecting point6 of the stiffening segment and soldering surfaces 8, without divertingforce onto the plug connector of the hybrid. Edge 16 of tin-coatedcopper layer 12, 13 facing end 3 of feed line segment 1 is provided witha notched rim, to prevent a break of printed circuit traces 7 in thetransitional area between the flexible conductor foil and the reinforcedconductor foil. In the exemplary embodiment shown here, the conductorfoil contacts a metallic housing wall in area a. Polyimide layer 11 andmetallic layers 12, 13 advantageously generate an abrasion protectioneffect for the conductor foil.

What is claimed is:
 1. A conductor foil for conductively connectingelectrical components, comprising:printed circuit traces insulated on anouter side of the conductor foil and applied on a non-conductive carrierfoil, the non-conductive carrier foil being elastically malleable; atleast one feed line segment; soldering surfaces coupled to the printedcircuit traces via the at least one feed line segment for soldering tothe electrical components; and at least one stiffening segment extendingaway from the at least one feed line segment, the at least onestiffening segment adapted for being coupled to a connecting pointoutside of the electrical components soldered to the soldering surfaces;wherein shaking stresses generated by vibrations on a movable end of theat least one feed line segment, which is not connected to the solderingsurfaces, are diverted away from the soldering surfaces and transmittedto the at least one stiffening segment and to said connecting point. 2.The conductor foil according to claim 1, further comprising:at least onereinforcing layer partly extending over the at least one stiffeningsegment and the at least one feed line segment in a common bonding area.3. The conductor foil according to claim 2, wherein an edge of the atleast one reinforcing layer is positioned toward the moveable end. 4.The conductor foil according to claim 2, wherein the at least onereinforcing layer includes at least one of a metallic layer and anon-conductive plastic layer applied onto the conductor foil.
 5. Theconductor foil according to claim 4, wherein the metallic layer iscomposed of a copper layer coated with a tin material.
 6. The conductorfoil according to claim 4, wherein the non-conductive plastic layer iscomposed of a polyimide material.
 7. The conductor foil according toclaim 1, wherein the connecting point provides a ground connection forthe electrical components.
 8. The conductor foil according to claim 1,wherein at least one of the soldering surfaces is coupled to theconnecting point via a foil segment, the foil segment including one ofthe printed circuit traces coupled to the at least one feed linesegment.
 9. The conductor foil according to claim 8, wherein at leastone of the soldering surfaces is coupled to a ground connection of theelectrical components, and wherein the printed circuit traces include agrounding printed circuit trace coupled to one of the solderingsurfaces.